Peat soil is an accumulation of partially decayed organic matter, primarily plant material like Sphagnum moss, which forms in waterlogged and acidic wetland environments such as bogs and fens. Consistently wet and oxygen-depleted conditions prevent the organic material from fully decomposing, allowing it to build up over thousands of years. Historically, peat was valued for its ability to retain water, its sterile nature, and its use as a soil amendment. While it gained widespread use in horticulture and as a fuel source, modern environmental science has illuminated the significant damage caused by its extraction and use. The controversies surrounding peat center on its global climate impact, practical performance limitations, and the destruction of the unique ecosystems from which it is harvested.
Peat Extraction and Global Climate Consequences
Peatlands are the largest natural terrestrial carbon store on the planet, holding more carbon than all other vegetation types, including the world’s forests, combined. These ecosystems store an estimated 550 to 600 gigatonnes of carbon, sequestered over millennia, making them a globally significant carbon sink. Carbon is stored because waterlogged conditions prevent oxygen from reaching the dead plant matter, halting decomposition.
When peat is extracted for commercial use, the peatland must first be drained, lowering the water table. This exposes the submerged organic material to the air. Oxygen initiates rapid decomposition by microbes, oxidizing the stored carbon. This process converts the long-sequestered carbon into greenhouse gases, primarily carbon dioxide, which are then released into the atmosphere.
Drained peatlands are a major source of greenhouse gas emissions, responsible for a disproportionate amount of global carbon dioxide releases. Emissions from these areas contribute nearly 5% of global anthropogenic carbon dioxide emissions annually. The destruction of this carbon sink converts it into a carbon source, releasing centuries of stored carbon and accelerating global warming.
Horticultural Drawbacks of Using Peat
Peat presents several practical performance challenges for gardeners. It is naturally highly acidic, often having a very low pH, making it unsuitable as a primary growing medium for many common garden plants that prefer neutral or alkaline soil conditions.
Another issue is peat’s extremely low nutrient content, often described as inert. Peat has a very low cation exchange capacity (CEC), meaning it is poor at holding onto nutrient ions like calcium, magnesium, and potassium. Plants grown in peat-heavy mixes must rely on frequent fertilization, as the medium provides little sustained nutrition.
The most frustrating practical drawback is water repellency, or hydrophobia, which occurs when peat dries out completely. If a peat-based mix becomes too dry, the fibers are exceptionally difficult to rewet. Water applied often runs down the sides of the pot instead of being absorbed, leaving the root ball dry.
Resource Depletion and Ecosystem Collapse
The accumulation of peat is an extremely slow geological process, making it functionally non-renewable on any human timescale. Peat forms at a rate of only a few millimeters per year, taking between 600 and 2,400 years to accumulate just one meter of depth. The rate of extraction far outpaces the rate of natural regeneration, as the peat harvested today took thousands of years to form.
Harvesting peat involves draining and strip-mining the bog, resulting in the destruction of a fragile and unique habitat. Peatlands are specialized ecosystems that support a specific biodiversity of highly adapted flora and fauna, including carnivorous plants, specialized mosses, birds, and unique insects.
When a peat bog is mined, the entire ecosystem is eliminated, leading to the collapse of the localized habitat and the loss of unique species. While restoration may be attempted, recovering the complex ecological function and stored carbon of an ancient peatland can take centuries. The physical removal of the material represents a permanent loss of a landscape feature that provided services like water filtration and flood minimization.